When a fence is being installed, it is desirable to position the posts vertically and the rails horizontally. While this can be done by eye, it is also common to use a simple carpenter's level that includes two spirit levels, one for determining a horizontal position and the other for determining a vertical position. The level is held against the post or rail by one hand while the other hand is used to adjust the rail or post to its proper position. The disadvantage is that there are times when the user requires the use of both hands and must set down the level with the result that the rail or post can be moved without there being any indication of the degree of horizontal or vertical movement.
Within the prior art there are many leveling devices that provide indications of both horizontal and vertical positions of an item being leveled or plumbed. U.S. Pat. No. 928,600 shows a simple carpenter's level having two vials at right angles for indicating horizontal and vertical lines. The device has a generally cubical body adapted to be held against or set upon the workpiece.
U.S. Pat. No. 3,826,013 discloses a device particularly useful with rods, which device includes two bulls-eye levels. The device uses right angle surfaces to position the device against the workpiece and the device is manually held in place.
U.S. Pat. Nos. 2,757,458, 3,664,754 and 4,295,279 describe strap on leveling devices attached to drills allowing the user free use of both hands for drilling vertical and horizontal holes. U.S. Pat. No. 3,832,782 shows a level having magnets located near deverging legs, which magnets allow the level to be magnetically mounted upon a magnetically attracted workpiece.
Perhaps the closest prior art patent is U.S. Pat. No. 4,168,578 which shows a level having two right angular members, the inner surfaces of which would be placed against a workpiece. Several spirit levels are mounted on the external surfaces of the members to indicate both horizontal and vertical positions. Magnetic strips are attached to the inner surfaces allowing the level to be attached to magnetically attractable workpieces to free up the user's hands. The patent also indicates that the device can be secured to objects which are not metal "with a pliable or elastic strap, cord, or tension spring wrapped around the object . . . " to free the user's hands.
As described below, the invention makes use of a well known type of separable fastener of the type disclosed in U.S. Pat. No. 3,009,235. Such fastener includes two pieces of base material one of which has a multiplicity of loops and the other of which has a multiplicity of hooks. The two pieces can be pressed together whereby the hooks and loops interengage and hold the two pieces together along with whatever the pieces are fastened to. Several patents disclose the use of such a fastener for diverse purposes. U.S. Pat. No. 3,321,068 uses the fastener to support a thermometer. U.S. Pat. No. 3,358,141 uses straps of the material to fasten a child to a board to immobilize the child. U.S. Pat. No. 3,387,341 uses such a fastener to support a pen or pencil.